Cyclone
Cyclones are large-scale storms characterized by low pressure in the center surrounded by circular wind motion (counter clockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere). Severe storms arising in the Atlantic waters are known as hurricanes, while those developing in the Pacific Ocean and the China seas are called typhoons. The precise classification (e.g., tropical depression, tropical storm, hurricane) depends on the wind force (Beaufort scale), wind speed, and manner of creation.
Hurricanes are powerful storms that form at sea with wind speeds of 74 miles per hour or greater. They are tracked by satellites from the moment they begin to form, so warnings can be issued three to four days before a storm strikes. A hurricane covers a circular area between 200 and 480 miles in diameter. In the storm, strong winds and rain surround a central, calm "eye," which is about 15 miles across. Winds in a hurricane can sometimes reach 200 miles per hour. However, the greatest damage to life and property is not from the wind but from tidal surges and flash flooding. Hurricanes are rated on a 1 to 5 scale, known as the Saffir-Simpson Scale. Category 3, 4 and 5 hurricanes are considered major storms. See Table 2 for the Saffir-Simpson Scale.
Owing to its violent nature, its potentially prolonged duration, and the extensive area that could be affected, the hurricane or cyclone is the most devastating of all storms. The hurricane season lasts from June 1 through November 30, but most occur in August and September. Scientists have developed a relatively good understanding of the nature of hurricanes through observation, radar, weather satellites, and computer models.
A distinctive characteristic of hurricanes is the increase in sea level, often referred to as the storm surge. This increase in sea level is the result of the low-pressure central area of the storm creating a vaccuum, the storm winds piling up water, and the tremendous speed of the storm. Rare storm surges have risen as much as 14 meters (45.9318 feet) above normal sea level. This phenomenon can be experienced as a large mass of sea water pushed along by the storm with great force. When it reaches land, the impact of the storm surge can be exacerbated by high tide, a low-lying coastal area with a gently sloping seabed, or a semi-enclosed bay facing the ocean.
The severity of a storm's impact on humans is exacerbated by deforestation, which often occurs as the result of population pressure. When trees disappear along the coastlines, the winds and the storm surges can enter the land with greater force. Deforestation on the slopes of hills and mountains increases the risk of violent flash floods and landslides caused by the heavy rain associated with tropical cyclones. At the same time, the beneficial effects of the rainfallreplenishment of the water resourcesmay be negated due to the inability of a forest ecosystem to absorb and retain water.
Deaths and injuries from hurricanes occur because victims fail to evacuate or take shelter, do not take precautions in securing their property despite adequate warning, and do not follow guidelines on food and water safety or injury prevention during recovery. Morbidity during the storm itself results from drowning, electrocution, lacerations or punctures from flying debris, and blunt trauma from falling trees or other objects. Heart attacks and stress-related disorders can arise during the storm or its aftermath. Gastrointestinal, respiratory, vector-borne, and skin disease as well as accidental pediatric poisoning can all occur during the period immediately following the cyclone. Injuries from improper use of chain saws or other power equipment, disrupted wildlife (e.g., bites from animals, snakes, or insects), and fires are common. Fortunately, the ability to detect and track storms has helped reduce morbidity and mortality in many countries.
Public health professionals work with local emergency management agencies to prepare people to evacuate and to turn off their utilities. To avoid injury, residents should be advised to use common sense and wear proper clothing, including long sleeved shirts, pants, and safety shoes or boots. Furthermore, they should learn proper safety precautions and operating instructions before operating gas-powered or electric chainsaws. People should use extreme caution when using electric chainsaws to avoid electrical shock and should always wear gloves and a safety face shield or eyeglasses when using any chainsaw. Evacuees should be advised against wading in water as there may be downed power lines, broken glass, metal fragments, or other debris beneath the surface.
When returning to their dwellings after a disaster, residents should check for structural damage and electrical or natural gas or propane tank hazards. They should return to homes during the daytime and only use battery-powered flashlights and lanterns to provide light rather than candles, gas lanterns, or torches.
During the recovery period, public health and local emergency management officials must ensure an adequate supply of safe water and food for the displaced population. In addition to offering acute emergency care, community plans should provide for the continuity of care for homeless residents with chronic conditions.
Conduct needs assessment for affected communities, including a review of public health infrastructure.
Establish active and passive surveillance systems for deaths, illness, and injuries.
Educate the public about maintaining safe and adequate supplies of food and water.
Establish environmental controls.
Monitor infectious disease and make determinations about needed immunizations (e.g., tetanus).
Institute multifaceted injury control programs.
Establish protective measures against potential disease vectors.
Monitor potential release of hazardous materials.
Assure evacuation plans for people with special needs in nursing homes, hospitals, and home care.
Work with local communities to improve building codes (e.g., developing improved designs for wind safety).
American Public Health Association © 2005 American Public Health Association
Cite this: Types of Disasters and Their Consequences - Medscape - Sep 20, 2005.
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